CN119542126A

CN119542126A - Multi-charged particle beam drawing method and multi-charged particle beam drawing device

Info

Publication number: CN119542126A
Application number: CN202411188273.3A
Authority: CN
Inventors: 松本裕史
Original assignee: Nuflare Technology Inc
Current assignee: Nuflare Technology Inc
Priority date: 2023-08-28
Filing date: 2024-08-28
Publication date: 2025-02-28
Also published as: JP2025032755A; TW202510035A; US20250079120A1; KR20250032929A

Abstract

The present invention provides a multi-charged particle beam drawing method and a multi-charged particle beam drawing device that suppress the influence of the Coulomb effect and improve the drawing accuracy. The multi-charged particle beam drawing method comprises: a process of grouping multiple beams into multiple beam groups; a process of determining the irradiation time of each beam of each emission; and an emission division process, wherein each emission is divided into multiple irradiation steps including irradiation steps of different irradiation times, and in a part of the divided multiple irradiation steps, multiple irradiation steps of a predetermined first irradiation time are grouped into a first group, and a group of irradiation steps whose total irradiation time of each irradiation step is determined to be the irradiation time of each beam. In the emission division process, based on a predetermined allocation order and the number of irradiation steps that become connected, the timing of the irradiation step of the first group of irradiation steps belonging to each of the multiple beam groups is determined so that the timing is different for each beam group.

Description

Multi-charged particle beam drawing method and multi-charged particle beam drawing device

Related application

The present application enjoys priority of Japanese patent application No. 2023-138217 (application date: 28 of 8 th year of 2023). The present application includes the entire content of the basic application by referring to the basic application.

Technical Field

The present invention relates to a multi-charged particle beam drawing method and a multi-charged particle beam drawing apparatus.

Background

With the high integration of LSI, the line width of circuits used for semiconductor devices is becoming finer year by year. In order to form a desired circuit pattern as a semiconductor device, a method of reducing and transferring a high-precision original pattern (also called a reticle, used in a mask, or particularly a stepper, a scanner) formed on a light shielding film or the like on a glass substrate onto a wafer using a reduction projection exposure apparatus is employed. In the production of a high-precision original pattern, a so-called electron beam lithography technique in which a resist pattern is formed by an electron beam drawing device is used. In addition, there is also a case where a so-called direct wafer patterning method is employed in which a pattern is formed on a resist coated on a wafer by an electron beam.

In a multibeam drawing device using a blanking aperture array substrate as one form of the multibeam drawing device, for example, electron beams emitted from 1 electron gun are passed through a shaped aperture array member having a plurality of openings to form a multibeam (a plurality of electron beams). A blanking aperture array substrate is downstream of the shaped aperture array member. The blanking aperture array substrate has electrode pairs (blankers) for deflecting the beams individually for each of the beams, and openings for passing the beams formed between the electrode pairs, and they are arranged in an array on the blanking aperture array substrate. The blanking aperture array substrate switches off and on blanking deflection of a passing beam by controlling electrode pairs corresponding to respective beams of the plurality of beams to the same potential or to mutually different potentials. Multiple beams formed by the shaped aperture array members pass through the pass-through holes between respective corresponding blankers of the blanker aperture array substrate. The optical barrel of the multibeam drawing device is configured to shield the electron beam deflected by the blanker, and irradiate the substrate with the electron beam not deflected.

The drawing device using a plurality of beams can radiate a larger number of beams at a time than the drawing device using 1 electron beam, and thus can greatly improve the throughput. On the other hand, since the total beam current amount can be set to be large, there is a possibility that the drawing accuracy due to the coulomb effect is deteriorated. Specifically, a deterioration in resolution of the beam, a beam position deviation on the surface of the sample, or a focus deviation may occur due to repulsive force between electrons. The coulomb effect occurs significantly in the optical system where the density of the electron beams is high, for example, at the intersection (cross server) where the beams are bunched to one point, but the coulomb effect at the intersection on the downstream side of the blanking aperture array substrate is not constant, and varies depending on the total current amount of the on beams in the beams.

As a countermeasure for deterioration of drawing accuracy due to coulomb effect, for example, a method of reducing the total current amount of the on beam has been proposed (refer to japanese patent application laid-open No. 2007-329220). This method is effective when the standby time for which the beam cannot be turned on in the emission period is longer than the time for which the beam is turned on for the reason that the beam control is not at high speed or the like, but if the drawing system is optimized so that the standby time for which the beam cannot be turned on becomes short, the effect thereof becomes small.

Disclosure of Invention

An aspect of the present invention provides a multi-charged particle beam drawing method and a multi-charged particle beam drawing apparatus that suppress the influence of coulomb effect and improve drawing accuracy.

A multi-charged particle beam drawing method according to an aspect of the present invention includes a step of discharging a plurality of charged particles, a step of grouping a plurality of beams constituting the plurality of beams into a plurality of beam groups, a step of determining an irradiation time of each of the plurality of beams emitted from each of the plurality of beams based on drawing pattern data, an emission dividing step of dividing each of the plurality of emissions into a plurality of irradiation steps including different irradiation times, a step of grouping a plurality of irradiation steps of a predetermined 1st irradiation time into a 1st group in a part of the plurality of irradiation steps after division, a step of selecting a group of irradiation steps of the irradiation time of each of the plurality of beams after a total of irradiation times of each of the irradiation steps is determined, and a step of switching on and off each of the plurality of beams to perform the plurality of emission of beams, wherein in the emission dividing step, the irradiation steps of the plurality of 1st irradiation steps belonging to each of the plurality of beam groups are determined based on a predetermined distribution order and the number of irradiation steps to be turned on, and the irradiation steps of the plurality of irradiation steps of 1st irradiation steps are not timed to each of the plurality of beam groups.

Drawings

Fig. 1 is a schematic view of a multi-charged particle beam drawing apparatus according to an embodiment of the present invention.

Fig. 2 is a top view of a shaped aperture array member.

Fig. 3 is a cross-sectional view showing a structure of a blanking aperture array substrate.

Fig. 4 is a schematic configuration diagram of a control circuit in the blanking aperture array substrate.

Fig. 5 is a block diagram of the input/output circuit and the cell array circuit.

Fig. 6 is a schematic configuration diagram of the separate blanking mechanism.

Fig. 7 is a diagram showing an example of an irradiation step in the 1 emission period.

Fig. 8 is a diagram showing an example of the beam-on timing.

Fig. 9 is a diagram showing a distribution sequence of the irradiation step.

Fig. 10 is a diagram showing an example of the beam-on timing.

Fig. 11 is a diagram showing an example of the beam-on timing.

Fig. 12 (a) to 12 (c) are diagrams showing examples of grouping of beam arrays.

Fig. 13 is a flowchart illustrating a drawing method.

Fig. 14 is a diagram illustrating a drawing operation.

Fig. 15 is a diagram showing a distribution sequence of the irradiation step.

Fig. 16 is a diagram showing an example of the beam-on timing.

Fig. 17 is a diagram showing a distribution sequence of the irradiation step.

Fig. 18 is a diagram showing an example of the beam-on timing.

Fig. 19 is a graph showing an example of beam current in the case where the shift of the beam on timing is performed and in the case where the shift of the beam on timing is not performed.

Detailed Description

Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the embodiment, a structure using an electron beam as an example of a charged particle beam will be described. However, the charged particle beam is not limited to an electron beam, and may be an ion beam.

Fig. 1 is a schematic configuration diagram of a drawing device according to the embodiment. As shown in fig. 1, the drawing device 100 includes a drawing unit 150 and a control unit 160. The drawing device 100 is an example of a multi-charged particle beam drawing device. The drawing unit 150 includes an electronic barrel 102 and a drawing chamber 103. An electron gun 201, an illumination lens 202, a shaped aperture array member 203, a blanking aperture array substrate 204, a reduction lens 205, a limiting aperture member 206, an objective lens 207, and a deflector 208 are disposed in the electron column 102.

An XY stage 105 is disposed in the drawing chamber 103. On the XY stage 105, a substrate 101 to be drawn is disposed. A resist exposed by an electron beam is coated on the upper surface of the substrate 101. The substrate 101 is, for example, a mask blank or a semiconductor substrate (silicon wafer) processed by a semiconductor device. Further, a mirror 210 for stage position measurement is disposed on the XY stage 105.

The control unit 160 includes a control computer 110, a deflection control circuit 130, a table position detector 139, and a storage unit 140. The storage unit 140 receives drawing data from the outside and stores the drawing data. In the drawing data, information of a plurality of graphic patterns for drawing is defined. Specifically, a graphics code, coordinates, a size, and the like are defined for each graphics pattern. Other information, for example, control information of the irradiation amount may be additionally defined in the drawing data.

The control computer 110 includes an area density calculating unit 111, an irradiation time calculating unit 112, a data processing unit 113, and a drawing control unit 114. Each part of the control computer 110 may be constituted by hardware such as a circuit or software such as a program for executing these functions. Or may be a combination of hardware and software.

The stage position detector 139 irradiates the mirror 210 with laser light, receives reflected light from the mirror 210, and detects the position of the XY stage 105 by laser interferometry.

Fig. 2 is a conceptual diagram showing the structure of the shaped aperture array member 203. As shown in fig. 2, the molded aperture array member 203 is a plate-like member, and a plurality of openings 203a are formed in the surface of the molded aperture array member 203 along the longitudinal direction (y-direction) and the transverse direction (x-direction). The openings 203a are preferably formed in a rectangular shape having the same or substantially the same size and shape, for example. The shape of each opening 203a may be circular.

The electron beam 200 emitted from the electron gun 201 (emission unit) illuminates the shaped aperture array member 203 through the illumination lens 202. The electron beam 200 illuminates the area in the shaped aperture array member 203 that contains all of the openings 203 a. A part of the electron beams 200 pass through the plurality of openings 203a of the shaping aperture array part 203, and the remaining beams are blocked by the shaping aperture array part 203, thereby forming a plurality of electron beams, that is, a plurality of beams 20a to 20e. The shape of each of the bundles is rectangular, for example, in accordance with the shape of the opening 203a of the shaped aperture array member 203.

As shown in fig. 3, the blanking aperture array substrate 204 includes a support table 204a and a semiconductor substrate 204b made of silicon or the like provided on the support table 204 a. The center portion of the semiconductor substrate 204b is cut thin from the back surface side, and is processed into a thin film region 204c. The periphery surrounded by the diaphragm region 204c is an outer peripheral region having a relatively thick film thickness, and the semiconductor substrate 204b is held on the support table 204a via the back surface of the outer peripheral region. The center portion of the support table 204a is open, and the position of the membrane area 204c is located in the area of the opening of the support table 204 a.

In the diaphragm region 204c, a plurality of beam passing holes H are formed in correspondence with the arrangement positions of the plurality of openings 203a of the shaped aperture array member 203. In each passing hole H, a blanking device 50 composed of a pair of two electrodes 51, 52 is arranged, and 1 bundle of the multiple bundles passes between the pair of electrodes and through the passing hole H. The blanking unit 50 switches off/on of deflection of the beam passing through the passing hole H by grounding one electrode 52 to be held at the ground potential and switching the other electrode 51 to the ground potential or a potential other than the ground potential. Thus, the blanking unit 50 performs blanking control to set the plurality of bundles to a certain state of bundle on and bundle off, respectively. The principle of the blanking control is explained below.

When 1 beam of the plurality of beams is controlled to be in the beam-on state, the opposing electrodes 51 and 52 of the blanker 50 are controlled to be at the same potential, and the blanker 50 does not deflect the beam passing through the passing hole H. When the beam-off state is controlled, the electrodes 51 and 52 of the blanker 50 are controlled to be at different potentials from each other, and the blanker 50 deflects the beam passing through the pass-through hole H.

The bundles 20a to 20e passing through the blanking aperture array substrate 204 are reduced by the reduction lens 205, and travel toward the central opening formed on the limiting aperture part 206.

Here, the beam controlled to the beam-off state is deflected by the blanker 50, and is shielded by the limiting aperture member 206 due to a track outside an opening passing through the limiting aperture member 206. On the other hand, the beam controlled to the beam on state passes through the opening of the limiting aperture member 206 since it is not deflected by the blanker 50. The trajectory of the beam is adjusted in advance by a collimator coil (not shown) so that the beam controlled to be in the beam-on state is positioned within the opening of the limiting aperture member 206. In fig. 1, the trajectory of the bundles is adjusted so that the bundles in the bundle on state are concentrated at 1 point at the position of the restricting aperture member 206, but it is preferable that the calibration coil is adjusted so that the 1 point is located at the center portion of the opening of the restricting aperture member 206. In this way, the on/off state of each of the multiple beams is controlled by a combination of the on/off operation of the deflection of the blanker 50 and the shielding of the beams by the limiting aperture. Namely, blanking control is performed.

As described above, the blanking aperture array substrate 204 individually performs blanking control for each of the multiple beams 20 using the multiple blankers 50. That is, the beam on/off state can be switched independently for each of the plurality of beams 20. In the irradiation step described later, from a state in which all of the plurality of beams are controlled to be in a beam-off state, only a predetermined beam blanking is controlled to be in a beam-on state, and after a predetermined time has elapsed, all of the plurality of beams are controlled to be in a beam-off state. By such blanking control, only the selected beam of the plurality of beams can be controlled to be in the beam-on state for a predetermined time.

The plurality of objective lenses 207 passing through the limiting aperture member 206 are focused, and a pattern image as a desired reduction ratio is formed on the substrate 101. Desirably, the plurality of bundles are arranged on the substrate 101 at a pitch obtained by multiplying the arrangement pitch of the plurality of openings 203a of the shaped aperture array member 203 by the above-described desired reduction ratio. Each beam (the whole of the plurality of beams in which the beam is turned on) having passed through the limiting aperture member 206 is deflected together in the same direction by the deflector 208, and irradiated onto a desired position on the substrate 101 while focusing on the surface of the substrate 101.

Irradiation of the substrate 101 by a plurality of beams can be performed both in a state where the XY stage 105 is stationary and in a state where it is continuously moving. When the XY table 105 is continuously moved, the table position detector 139 measures the amount of change in the table position, and as a result, the deflector 208 is used to continuously change the position of the plurality of beams so as to follow the movement of the XY table 105. Which is referred to as stage tracking deflection. The position of the multiple beams on the substrate 101 can be fixed by tracking deflection by the stage. At least during the irradiation of the beam onto the substrate 101, the stage tracking deflection is controlled so that the positions of the multiple beams on the substrate 101 are fixed.

The blanking aperture array substrate 204 includes a control circuit for applying a desired voltage to the blanking device 50, in addition to the blanking device 50 and the through-hole H described above. As shown in fig. 4, the control circuit includes an input/output circuit 31 and a cell array circuit 34.

As shown in fig. 5, the cell array circuit 34 is provided with a plurality of units constituting an individual blanking mechanism 40 for driving the blanker 50. Fig. 5 shows an example of a blanking aperture array substrate having 26144 cell array circuits each including 512 rows and 512 columns and a blanking unit. 1 individual blanking mechanism 40 drives 1 blanker 50. The input/output circuit 31 outputs the data received from the deflection control circuit 130 to the cell array circuit 34. For example, the input-output circuit 31 has an input-output circuit 31a that outputs data to the individual blanking mechanism 40 arranged on one half side of the cell array circuit 34 and an input-output circuit 31b that outputs data to the individual blanking mechanism 40 arranged on the other half side.

The input/output circuit 31 is provided with a plurality of selectors 320 (multiplexers). The selector 320 receives irradiation time control data defining on/off of each beam via the amplifier 310, and outputs the irradiation time control data from the corresponding output line. A plurality of individual blanking mechanisms 40 are connected in series on each output line.

The selector 320 has, for example, 8 output lines row1 to row8, and 256 individual blanking mechanisms 40 are connected to each output line. By disposing 64 selectors 320 in each of the input/output circuits 31a and 31b, irradiation time control data can be transferred to 512×512 individual blanking mechanisms 40 constituting the cell array circuit 34.

As shown in fig. 6, the individual blanking mechanism 40 has a shift register 41, a pre-buffer 42, a buffer 43, a data register 44, a NAND circuit 45, and an amplifier 46. The SHIFT register 41 transfers data output from the SHIFT register of the preceding stage unit to the SHIFT register of the succeeding stage unit in accordance with a clock Signal (SHIFT).

The pre-buffer 42 stores the irradiation time control data for the cell outputted from the shift register 41 in accordance with the clock signal (LOAD 1).

The buffer 43 takes in and holds the output value of the pre-buffer 42 in accordance with the clock signal (LOAD 2).

The data register 44 takes in and holds the output value of the buffer 43 in accordance with the clock signal (LOAD 3).

For the NAND circuit 45, an output signal of the data register 44 and an emission ENABLE signal (shot_enable) are input. The output signal of the NAND circuit 45 is given to an electrode 51 of the blanking unit 50 via an amplifier 46 (driver amplifier).

When the output signal and the emission enable signal of the data register 44 are both at High potential (High), the output of the NAND circuit 45 is at Low potential (Low), the electrode 51 and the electrode 52 are at the same potential, and the blanker 50 does not deflect the beam, so that the beam is turned on. When at least one of the output signal of the data register 44 and the emission enable signal is at a Low potential (Low), the output of the NAND circuit 45 is at a High potential (High), the electrodes 51 and 52 are at different potentials, and the blanker 50 deflects the beam and turns it off.

The emission enable signal is input to the NAND circuits 45 of all the individual blanking mechanisms 40, and by setting the emission enable signal to Low potential (Low), all the bundles can be set to off regardless of the output signal of the data register 44.

In a state where the emission enable signal is maintained at a High potential (High), on/off of the beam is switched by the output of the data register 44. That is, the beam is turned on when the irradiation time control data is 1 (High), and is turned off when the irradiation time control data is 0 (Low).

In order to form a resist pattern in a desired size by exposure of a resist, the irradiation amount needs to be controlled to an appropriate value. That is, in the blanking control, not only the on/off of the beam needs to be switched, but also the time for which the beam is turned on needs to be controlled. Since the blanking control is performed by a logic circuit, that is, a digital circuit, the irradiation time is expressed by an integer value. For example, the irradiation time T is divided by the quantization unit Δ, and the stepwise (Japanese: scale) irradiation time N is calculated. The quantization unit Δ can be variously set, but the maximum irradiation time obtained by multiplying the maximum value of the stepwise irradiation time N by the quantization unit Δ is set to be larger than the maximum value of the irradiation time required for exposure. The quantization unit Δ is set to, for example, 1 ns.

In multibeam drawing, since some of the multibeams are positioned in the interior of the pattern and other beams are positioned at the end of the pattern or in an area without the pattern, the irradiation time control data allocated to each of the bundles is not the same in all the bundles. Thus, it is necessary to independently control the irradiation time of each of the plurality of beams. As one mode of such control, a circuit of the blanking plate 204 shown in fig. 4 is used, and 1 emission is divided into a plurality of irradiation steps having different lengths, and each beam is controlled so as to be turned on at the irradiation step required to obtain a desired exposure time. Therefore, the stage value N is converted into a binary number of the number N, and the length of the irradiation step corresponding to each bit of the binary number of the number N, that is, the time when the beam is turned on is set to be the time obtained by multiplying the decimal number corresponding to each bit of the binary number by Δ.

For example, if the irradiation time is stepwise n=50 and the number of bits n=8, the irradiation time control data is uniquely determined to be "00110010" based on 50=2 ⁵+2⁴+2¹ which is a relationship in which the 10-ary number is represented by the sum of the powers of 2. Similarly, if the stepwise irradiation time n=100 and the number of bits n=8, the irradiation time control data becomes "01100100".

An irradiation step in which the 1 st bit corresponds to an irradiation time 1 Δ from the lower bit of the irradiation time control data. An irradiation step in which the 2 nd bit corresponds to the irradiation time 2Δ from the lower bit of the irradiation time control data. An irradiation step in which the 3 rd bit corresponds to the irradiation time 4Δ from the lower bit of the irradiation time control data. An irradiation step in which the 4 th bit corresponds to the irradiation time 8Δ from the lower bit of the irradiation time control data. An irradiation step in which the 5 th bit corresponds to the irradiation time 16Δ from the lower bit of the irradiation time control data. An irradiation step in which the 6 th bit corresponds to the irradiation time 32Δ from the lower bit of the irradiation time control data. An irradiation step in which the 7 th bit corresponds to the irradiation time 64Δ from the lower bit of the irradiation time control data. An irradiation step corresponding to an irradiation time 128 Δ from the lower bit of the irradiation time control data at bit 8. That is, 1 emission is divided into irradiation steps of the same number of times as the number of bits (number of bits) n of the irradiation time control data, and each irradiation step has an irradiation time of Δx2 ^k－1 (k=1, 2.

Fig. 7 shows an example of an irradiation step of 1 emission in the case where the number of bits n=8 and the quantization unit Δ=1 ns. In this example, each irradiation step is performed sequentially from the irradiation step having a longer irradiation time. The 1 st irradiation step is irradiation with an irradiation time of 128 ns. The 2 nd irradiation step is irradiation with an irradiation time of 64 ns. The 3 rd irradiation step is irradiation with an irradiation time of 32 ns. The 4 th irradiation step is irradiation with an irradiation time of 16 ns. The 5 th irradiation step is irradiation with an irradiation time of 8 ns. The 6 th irradiation step is irradiation with an irradiation time of 4 ns. The 7 th irradiation step is irradiation with an irradiation time of 2 ns. The 8 th irradiation step is irradiation with an irradiation time of 1 ns. Further, the total irradiation time is not changed even if the irradiation steps are replaced, and thus the steps may be performed in a different order from that of fig. 7.

In the case where n=100, the irradiation time control data is "01100100", and as shown in fig. 8, the beam is controlled to be on in the irradiation step of the 2 nd (64 ns), 3 rd (32 ns), 6 th (4 ns), and the beam is controlled to be off in the irradiation step of the 1 st, 4 th, 5 th, 7 th, 8 th.

As described above, the required irradiation time is set for each of the plurality of beams. In a certain emission, when a certain staged irradiation time, for example, n=100 is set for a certain beam, a staged irradiation time, for example, n=50, different from that for other beams is set. The irradiation steps in the 1-emission period are performed simultaneously for all the multiple beams, but each beam is independently controlled to be on or off in each irradiation step. That is, for the beam with the staged irradiation time of n=100 and the beam with n=50, the beam on and off in each irradiation step are controlled with different irradiation time data, that is, with different combinations of beam on and beam off corresponding to each irradiation step. In this way, the irradiation time of each of the plurality of beams in the 1 emission period is controlled independently for each beam.

In the drawing by electron beam irradiation, when a pattern is irradiated with a uniform irradiation amount, a problem of so-called proximity effect occurs in which the pattern size becomes thicker at a position where the density of the pattern is high. This is because electrons passing through the resist coated on the upper surface of the substrate to be drawn are backscattered by the substrate and re-enter the resist, and secondary resist sensitization occurs. In order to correct the proximity effect, a method of correcting the irradiation amount based on the pattern density around the beam irradiation position is used.

In this method, the higher the pattern density is, the smaller the irradiation amount is so that the sum of the light-sensitive amount of the resist, i.e., the primary light-sensitive amount by irradiation and the secondary light-sensitive amount by back scattering, becomes constant regardless of the pattern density. As a result, the pattern size can be made constant regardless of the pattern density. The amount of secondary light sensing due to back scattering is about half the amount of primary light sensing due to irradiation, and in this case, half the irradiation amount of the pattern having a density of 0% is used in the pattern having a density of 100%. The proximity effect correction irradiation amount D is given by the following equation, for example.

Here, D _base is the reference dose, η is the backscatter coefficient, and U is the average pattern density at the irradiation position.

In multi-beam drawing, particularly multi-beam drawing using a plurality of multi-beams, there may be a case where both a region having a higher density and a region having a lower density exist among regions to be drawn by the multi-beams. Therefore, it is necessary to set the maximum time of emission and the cycle time of emission to be longer than the irradiation time after the proximity effect correction of the region having a density of zero so that the drawing can be performed even if there is a region having a density of zero at all times, that is, the region having the longest irradiation time after the proximity effect correction. In order to simplify the control, there are many cases where a table speed at which drawing in the cycle time of emission in a region where the density is zero can be performed is calculated and so-called table constant-speed travel is used in which the table speed is fixed at the calculated table speed.

As a result, the light beam exposing the region having the lower pattern density is turned on for the most part of the emission period, and the light beam exposing the region having the higher pattern density is turned on only for a part of the emission period, and particularly, the light beam exposing the region having the pattern density of 100% is turned on only for about half of the emission period, and is controlled to be turned off for the rest of the time.

The multi-beam drawing device is characterized in that a large number of beams are used to increase the total current amount of the plurality of beams, thereby drawing a low-sensitivity resist at a high speed. On the other hand, if the total current amount of the plurality of beams becomes large, there is a principle problem that the resolution of the beams or the resolution of the drawn pattern is deteriorated by the coulomb effect. In the present embodiment, in order to alleviate deterioration of drawing accuracy due to coulomb effect without reducing drawing speed, control is performed to shift timings at which the respective beams of the plurality of beams are turned on in the emission period. Further, as described above, by using a short beam on time in the emission period in the region where the proximity effect density is high and performing 1 emission by a plurality of irradiation steps, it is possible to perform blanking control of the plurality of beams without greatly extending the emission period or greatly reducing the drawing speed, so as to reduce the total amount of current of the plurality of beams in the on state.

In the present embodiment, a plurality of (m) irradiation steps with an irradiation time T1 and a plurality of irradiation steps with an irradiation time less than T1 are set in 1 emission period. The irradiation time control is preferably simplified if the irradiation time of each irradiation step is proportional to the power of 2, so an example of this case will be described. The irradiation steps with irradiation times less than T1 differ from each other in irradiation time. The plural beams are grouped into m groups, and in each group, the distribution order of the irradiation steps with the irradiation time T1 is changed, and irradiation is performed in the distribution order. The storage unit 140 stores group information indicating which group each bundle belongs to.

Such an irradiation step may be generated by dividing a part of the irradiation steps from a group of a plurality of irradiation steps of an irradiation time of a power of 2. For example, from the plurality of irradiation steps shown in fig. 7, the 1 st irradiation step of the irradiation time 128ns is divided into two irradiation steps of the irradiation time 64 ns. By this division, the number of irradiation steps is increased, but in order not to reduce the drawing speed, it is preferable to delete the irradiation step (of irradiation time 1 ns) of which the irradiation time is shortest so as not to increase the number of bits (number of bits) of the irradiation time control data. Thus, as shown in fig. 9, the 1 st to 3 rd irradiation steps are 64ns irradiation. The 4 th irradiation step was an irradiation of 32 ns. The 5 th irradiation step was 16ns irradiation. The 6 th irradiation step was 8ns irradiation. The 7 th irradiation step was an irradiation of 4 ns. The 8 th irradiation step was 2ns irradiation. In order to delete the irradiation step (of irradiation time 1 ns) of which irradiation time is shortest, the quantization unit Δ may be set to 2ns which is2 times 1 ns.

Further, in order to shift the timing of turning on the plurality of beams, the plurality of beams are classified into a plurality of groups, and blanking control is performed by a different method for each group. For example, in the example of fig. 9, the bundles are classified into 3 groups a to C, the group a bundles are assigned No. 1 in the order of 1 st irradiation step, no. 2 in the order of 2 nd irradiation step, and No. 3 in the order of 3 rd irradiation step. The beam of group B has the assignment sequence of the 3 rd irradiation step as No. 1, the assignment sequence of the 1 st irradiation step as No. 2, and the assignment sequence of the 2 nd irradiation step as No. 3. The beam of group C has the assignment sequence of the irradiation step 2 as No. 1, the assignment sequence of the irradiation step 3 as No. 2, and the assignment sequence of the irradiation step 1 as No. 3.

For example, in the case where the irradiation time of 1 emission is 80ns, since the quantization unit is 2ns, the stepwise irradiation time is 40. In fig. 9, according to the relationship in which the 10-ary number is represented by the sum of the numbers of powers of 2 and the relationship of 40=2 ⁵+2³, the desired exposure time of 80ns can be obtained by performing exposure in 1 of the 3 irradiation steps of 64ns in irradiation time and in the irradiation step of 16ns in irradiation time. Here, when the above-described distribution sequence is set, the beam of group a is turned on in the 1 st irradiation step and the 5 th irradiation step as shown in fig. 10. The beam of group B is turned on in the 3 rd irradiation step and the 5 th irradiation step. The beam of group C is turned on in the irradiation step of the 2 nd time and the irradiation step of the 5 th time. The irradiation steps of the beams of groups a to C with respect to the irradiation time of 64ns are turned on at mutually different timings, so that the amount of current to turn on the beams can be reduced.

For example, in the case where the irradiation time of 1 emission is 180ns, since the quantization unit is 2ns, the stepwise irradiation time is 90. According to the relationship of 90=2 ⁶+2⁴+2³+2¹, the beam becomes on in 2 out of the irradiation steps of the irradiation time 64ns of fig. 9 and the irradiation steps of the irradiation times 32ns, 16ns, and 4ns within 1 emission period. When the above-described distribution order is set, the beam of group a is turned on in the 1 st, 2 nd, 4 th, 5 th, and 7 th irradiation steps as shown in fig. 11. The beam of group B is turned on in the 1 st, 3 rd, 4 th, 5 th and 7 th irradiation steps. The beam of group C is turned on in the irradiation steps of the 2 nd, 3 rd, 4 th, 5 th and 7 th times. The irradiation step with the irradiation time of 64ns is two groups to be turned on at the same time, and 3 groups are not turned on at the same time, so that the amount of current of the turned-on beam can be reduced.

Specifically, when all of the plurality of beams are irradiated for an irradiation time of 180ns, the total current of the on beams averaged in the emission period can be reduced to a level at which the number of beams turned on in each irradiation step is weighted by the irradiation time of each irradiation step and averaged to obtain a value (64×2+64×2+64×2+32×3+16×3+4×3)/(64+64+64+32+16+4)/3=73%. In the example of fig. 11, when the irradiation time after the proximity effect correction of the pattern density 0 region is set to 250ns, the irradiation time of the pattern density 40% region is about 180 ns. That is, in the region where the pattern density is 40% or more, since the pattern density is high, the number of the bundles to be turned on and the amount of current of the bundles to be turned on are large, but in the present embodiment, the average value of the total current of the turned-on bundles in the emission period can be reduced by 30%.

By setting the distribution order of the irradiation steps to be different for each group in this way, the timings at which the plurality of beams are turned on can be shifted from group to group, the average value in the emission period of the total current of the turned-on beams can be reduced, the influence of the coulomb effect can be reduced, and the drawing accuracy can be improved. Further, as shown in fig. 7 and 9, since the number of irradiation steps constituting 1 emission and the total irradiation time of the respective irradiation steps are not changed, the emission period and the drawing time are not prolonged. That is, the average value in the emission period of the total current of the on-beams of the plurality of beams can be reduced without extending the drawing time.

Fig. 12 (a) to 12 (C) show examples of grouping a plurality of bundles into groups a to C. Fig. 12 (a) to 12 (c) show an 8×8 beam array for convenience of explanation. It is preferable to group so that no bias of the beam current to turn on the beam occurs. Therefore, it is preferable to group the bundles of groups a to C in order as shown in fig. 12 (a) and 12 (b) compared to the group shown in fig. 12 (C). In fig. 12 (a), the beams adjacent in the x-direction and the y-direction belong to mutually different groups. In fig. 12 (b), the beams adjacent in the x direction belong to mutually different groups.

Next, a pattern drawing method according to the present embodiment will be described with reference to a flowchart shown in fig. 13. In the pattern area density calculating step (step S1), the area density calculating unit 111 virtually divides the drawing region of the substrate 101 into a plurality of mesh regions. The size of the grid region is, for example, the same size as the size of each of the bundles constituting the plurality of bundles, and each grid region becomes a pixel (unit irradiation region). The area density calculating unit 111 reads out the drawing data from the storage unit 140, and calculates the pattern area density ρ of each pixel using the pattern defined by the drawing data.

In the irradiation time calculation step (step S2), the irradiation time calculation unit 112 multiplies the pattern area density ρ by the reference irradiation amount D ₀ and a correction coefficient for correcting the proximity effect or the like, and calculates the irradiation amount of the beam irradiated to each pixel. The irradiation time calculation unit 112 divides the irradiation amount by the current density, and calculates the irradiation time.

In the irradiation time control data generation step (step S3), the data processing unit 113 assigns irradiation times to a plurality of irradiation steps in consideration of the assignment order of the irradiation steps, and generates irradiation time control data. For example, the data processing unit 113 divides the irradiation time by the quantization unit, and calculates the stage value t (the integral irradiation time). In the example shown in fig. 9, the data processing unit 113 obtains, as the irradiation time control data, a row b _k (k=1, 2,..7) of ON/OFF (ON/OFF) flags corresponding to the respective T _k for the row T _k(2⁵,2⁵,2⁵,2⁴,2³,2²,2¹,2⁰.

B ₁,b₂,b₃ as the high-order bit is determined by the value of m=floor (T/T _M) obtained from the corresponding time T _M＝T₁＝T₂＝T₃＝2⁵ and the allocation order of the irradiation steps for each group. But m is a number not exceeding 3. B ₄,b₅,b₆,b₇,b₈ as a low order bit is determined by binary-converting the integer T-mxt _M. More generally, even when a part of the series T _k is not a power of 2, the irradiation amount control data b _k can be obtained from T using the following expression or the like.

When the quantization unit Δ of the irradiation time is determined so that the irradiation time is shorter than the total value of the irradiation times in the irradiation steps, the bit sequence b _k is determined based on the phase value t of the irradiation time.

In the data transfer step (step S4), the drawing control unit 114 outputs irradiation time control data to the deflection control circuit 130. The deflection control circuit 130 outputs irradiation time control data to the blanking aperture array substrate 204. The input/output circuit 31 of the blanking aperture array substrate 204 transfers the irradiation time control data to the corresponding individual blanking mechanism 40.

In the individual blanking mechanism 40, the irradiation time control data is transferred to the succeeding buffer 1 bit at a time in accordance with the clock signal. The data corresponding to the irradiation time of each irradiation step is transferred, and the on/off of the beam in each irradiation step is switched in accordance with the irradiation time control data stored in the buffer 44 of the last stage. If 1 shot of the shot step is performed, shot time control data of the next shot step is transferred to each of the buffers and the last-stage buffer 44. In this way, the irradiation time control data of each beam in each irradiation step is followed, and the on/off of each beam is switched.

In the drawing step (step S5), the drawing control unit 114 controls the drawing unit 150 to execute drawing processing. The drawing control unit 114 controls the deflector 208 using the deflection control circuit 130, and positions the plurality of beams so that each of the plurality of beams irradiates each pixel corresponding to the transferred data. After the positioning is completed, the drawing control unit performs the irradiation step using the deflection control circuit 130, and performs blanking control so that each of the plurality of beams is irradiated with a predetermined irradiation amount of the corresponding pixel. When the irradiation step constituting 1 shot is completed, the data transfer step and the drawing step are performed, and the irradiation of the next pixel group is performed.

As described above, by repeating the steps of fig. 13, the drawing unit 150 performs the drawing operation for drawing the drawing region in the raster scan system using a plurality of beams.

Fig. 14 is a conceptual diagram for explaining the drawing operation. As shown in fig. 14, the drawing region 80 of the substrate 101 is virtually divided into a plurality of stripe regions 82 in a short stripe shape with a predetermined width in the y direction (1 st direction), for example. First, the XY stage 105 is moved, and the irradiation region 84 irradiated by irradiation with a plurality of beams at a time is adjusted so as to be positioned at the left end of the 1 st stripe region 82, and drawing is started.

When drawing the 1 st stripe region 82, the XY table 105 is moved in the-x direction, whereby the drawing is relatively advanced in the +x direction. In the drawing, the plurality of beams are deflected at least in the Y direction by the deflector, whereby pixels to which the plurality of beams are exposed are switched. By repeating the switching of the exposure pixels and the exposure operation, a plurality of beams expose all pixels defined in the stripe region 82. The XY stage 105 is continuously moved at a predetermined speed. At this time, the table speed is set in a range in which the drawing operation described above is possible. After the drawing of the 1 st stripe region 82 is completed, the stage position is moved in the-y direction, and the beam array 84 is adjusted so as to be positioned at the right end of the 2 nd stripe region 82. Next, the XY stage 105 is moved in the +x direction, and drawing is performed in the-x direction.

In the 3 rd stripe region 82, the drawing is performed in the +x direction, and in the 4 th stripe region 82, the drawing is performed in the-x direction. By drawing while alternately changing the orientation, the drawing time can be shortened. The stripe regions 82 may be drawn in the same direction.

In the present embodiment, instead of changing the number of irradiation steps, a plurality of irradiation steps having the same irradiation time are set in 1 emission period, and the plurality of irradiation steps are classified into a plurality of groups, and the distribution order of the irradiation steps is changed between the groups. In this way, in the irradiation step of at least a part of the 1 emission period, the timings at which the beams are controlled to be on are shifted among the plurality of groups of the plurality of beams, so that the average total current of the on beams in the emission period can be reduced, the influence of the coulomb effect can be reduced, and the drawing accuracy can be improved.

In the present embodiment, the number of groups obtained by grouping a plurality of groups may be set to 2 instead of 3 in fig. 9. In this case, the group a and the group B are set, the group a beam has the assignment sequence of the 1 st irradiation step as No. 1, the assignment sequence of the 2 nd irradiation step as No. 2, the assignment sequence of the 3 rd irradiation step as No. 3, the group B beam has the assignment sequence of the 3 rd irradiation step as No. 1, the assignment sequence of the 1 st irradiation step as No. 2, and the assignment sequence of the 2 nd irradiation step as No. 3. When the irradiation time of 1 or two of the 1 st, 2 nd, and 3 rd irradiation steps is used, control is performed so that the timings of part of the irradiation steps of the group a and the group B are shifted.

The number of bits of irradiation time control data may be increased, and the number of irradiation steps for the same irradiation time may be increased, so that the timing of turning on the beam may be shifted with good efficiency.

In this embodiment, for example, as shown in fig. 15, the number of bits (bit number) of the irradiation time control data is increased from 8 bits to 10 bits in fig. 7, the quantization unit Δ is set to 2ns, the 1 st irradiation step is set to 64ns irradiation, and the 2 nd to 6 th irradiation steps are set to 32ns irradiation. The 7 th irradiation step was 16ns irradiation. The 8 th irradiation step is 8ns irradiation. The 9 th irradiation step was an irradiation of 4 ns. The 10 th irradiation step was 2ns irradiation. The 10 irradiation steps correspond to the irradiation steps after decomposing the 1 st irradiation step of the irradiation time 128ns into 4 irradiation steps of the irradiation time 32ns in the 8 irradiation steps of fig. 7. Accordingly, the total value of the irradiation times in each irradiation step in fig. 15 is 255ns, which is the same as in fig. 7. However, since the number of drawing steps increases and the amount of irradiation time data transferred to the blanking aperture increases at the time of drawing, the overhead time of drawing such as the data transfer time increases, and the drawing time is longer than the case where the irradiation time control data is 8 bits.

In this embodiment, the multiple beams are classified into two groups A, B, and the distribution order of the irradiation steps of the 2 nd to 6 th times is changed between the group a and the group B. For example, the beam of group a has an assignment sequence of irradiation steps of No. 1, an assignment sequence of irradiation steps of No. 3, an assignment sequence of irradiation steps of No. 4, an assignment sequence of irradiation steps of No. 3, an assignment sequence of irradiation steps of No. 5, an assignment sequence of irradiation steps of No. 4, and an assignment sequence of irradiation steps of No. 6. The beam of group B has the assignment sequence of the irradiation step of the 6 th time as No. 1, the assignment sequence of the irradiation step of the 5 th time as No. 2, the assignment sequence of the irradiation step of the 4 th time as No. 3, the assignment sequence of the irradiation step of the 3 rd time as No. 4, and the assignment sequence of the irradiation step of the 2 nd time as No. 5.

For example, in the case where the irradiation time of 1 shot is 180ns, the beam is turned on in the irradiation step of the irradiation time 64ns, the irradiation step of the irradiation time 32ns, the irradiation step of the irradiation time 16ns, and the irradiation step of the irradiation time 4ns in 1 shot period.

When the above-described distribution order of the irradiation steps is set, the beam of group a is turned on in the 1 st to 4 th irradiation steps, the 7 th irradiation step, and the 9 th irradiation step as shown in fig. 16. The beam of group B is turned on in the 1 st irradiation step, the 4 th to 7 th irradiation steps, and the 9 th irradiation step. The irradiation step of the beam of group A, B with respect to the irradiation time of 32ns is simultaneously turned on only 1 time, and is turned on at different timings except for it, so that the amount of current to turn on the beam can be reduced. In this example, the number of groups obtained by grouping a plurality of groups is set to 2, but may be set to 3. For example, group C may be added to group A, B of fig. 15, and the beam of group C may be set to No. 4 in the order of assignment of the irradiation step 2, no. 5 in the order of assignment of the irradiation step 3, no. 1 in the order of assignment of the irradiation step 4, no. 2 in the order of assignment of the irradiation step 5, and No. 3 in the order of assignment of the irradiation step 6.

The number of bits of irradiation time control data can be increased to extend the emission period, and the timing at which the beam is turned on can be shifted more efficiently.

For example, as shown in fig. 17, the number of bits (bit number) of the irradiation time control data is 14, the quantization unit Δ is 2ns, and the irradiation steps of 1 to 6 times are 32 ns. The 7 th and 11 th irradiation steps become 16ns irradiation. The 8 th and 12 th irradiation steps become 8ns irradiation. The 9 th and 13 th irradiation steps become 4ns irradiation. The 10 th and 14 th irradiation steps became 2ns irradiation. That is, 4 irradiation steps of irradiation times of 16ns, 8ns, 4ns, 2ns for two sets were set. Thus, the total value of the irradiation times of the respective irradiation steps is increased by 14ns from 255ns in fig. 7. That is, the transmission period becomes longer by 14ns, and the drawing time becomes longer.

The multiple beams are classified into two groups A, B, and the distribution sequence of the 1 st to 6 th irradiation steps is changed between the group A and the group B. For example, the beam of group a has an assignment sequence of irradiation steps 1, an assignment sequence of irradiation steps 2, an assignment sequence of irradiation steps 3, an assignment sequence of irradiation steps 4, an assignment sequence of irradiation steps 5, and an assignment sequence of irradiation steps 6, respectively, of 1 st, 2 nd, 3 rd, 4 th, and 5 th. The beam of group B has the assignment sequence of the irradiation step of the 6 th time as No.1, the assignment sequence of the irradiation step of the 5 th time as No. 2, the assignment sequence of the irradiation step of the 4 th time as No. 3, the assignment sequence of the irradiation step of the 3 rd time as No. 4, the assignment sequence of the irradiation step of the 2 nd time as No. 5, and the assignment sequence of the irradiation step of the 1 st time as No. 6.

In addition, the set of the irradiation steps of 7 to 10 times uses only the group A, and the set of the irradiation steps of 11 to 14 times uses only the group B.

For example, in the case where the irradiation time of 1 shot is 140ns, the beam is turned on in the irradiation step of 4 shots of 32ns, the irradiation step of 8ns, and the irradiation step of 4ns in 1 shot period.

When the above-described distribution order of the irradiation steps is set, the beam of group a is turned on in the 1 st to 4 th irradiation steps, the 8 th irradiation step, and the 9 th irradiation step as shown in fig. 18. The beam of group B is turned on in the 3 rd to 6 th irradiation step, the 12 th irradiation step, and the 13 th irradiation step.

The irradiation step of the beam of group A, B with respect to the irradiation time of 32ns is performed only 2 times simultaneously, and is performed at different timings other than that, so that the average value of the total current of the turned-on beams in the emission period can be reduced. As is clear from fig. 16 and 18, in the irradiation step of fig. 18, since the group A, B is provided with a set of irradiation steps having a short irradiation time, the time for simultaneously turning on the group a beam and the group B beam can be shortened more efficiently than in the irradiation step of fig. 16.

Fig. 19 shows the average value of the total current of the on-beam in the emission period when the on-timing of the beam is shifted as shown in fig. 9, 15, and 17 and when the on-timing of the beam is not shifted. It was confirmed that by performing the shift of the on timing of the beam, the average value of the total current of the on beam in the emission period was reduced.

Further, it was confirmed that the higher the pattern area density, the larger the amount of decrease in the average value of the full current of the on beam in the emission period. This is because the pattern area density is high, so that the irradiation amount is reduced by the proximity effect correction, the number of irradiation steps for turning off the beam in the 1-emission period is increased, and the on timing of the beam can be efficiently shifted between the irradiation steps.

In the above embodiment, the beam shaping and blanking control may be performed by blanking the opening of the aperture array substrate, and the shaped aperture array member may be removed.

The present invention is not limited to the above-described embodiments, and the constituent elements may be modified and embodied in the implementation stage within a range not departing from the gist thereof. Further, various inventions can be formed by appropriately combining a plurality of the constituent elements disclosed in the above embodiments. For example, some of the constituent elements may be removed from all of the constituent elements shown in the embodiment modes. Further, the constituent elements of the different embodiments may be appropriately combined.

Description of the reference numerals

40 Individual blanking mechanism, 50 blanker, 100 drawing device, 110 control computer, 111 area density calculating unit, 112 irradiation time calculating unit, 113 data processing unit, 114 drawing control unit.

Claims

1. A multi-charged particle beam characterization method, characterized in that:

have:

The process of emitting multiple beams of charged particles;

The step of grouping the plurality of bundles constituting the plurality of bundles into a plurality of bundle groups;

a step of determining the irradiation time of each of the plurality of beams emitted at each time according to the drawing pattern data;

an emission division step of dividing each of the above-mentioned emissions into a plurality of irradiation steps including irradiation steps of different irradiation times, grouping a plurality of irradiation steps of a predetermined first irradiation time into a first group in a part of the above-mentioned plurality of irradiation steps after the division, and selecting a group of irradiation steps that becomes the irradiation time of each of the above-mentioned beams after the total irradiation time of each irradiation step is determined; and

A process of performing the plurality of irradiation steps by switching each of the plurality of beams on and off to emit the plurality of beams;

In the emission splitting process, the timing of the irradiation steps of the first group of the plurality of irradiation steps belonging to each of the plurality of beam groups is determined based on a predetermined allocation order and the number of the irradiation steps to be turned on, so that the timing of the irradiation steps of the first group is different for each beam group.

2. The multi-charged particle beam drawing method according to claim 1, characterized in that:

The plurality of irradiation steps each include the first group and a second group of irradiation steps consisting of irradiation steps having an irradiation time shorter than the first irradiation time.

3. The multi-charged particle beam drawing method according to claim 2, characterized in that:

The first irradiation time is the longest irradiation time among the irradiation times in the plurality of irradiation steps.

4. The multi-charged particle beam drawing method according to claim 1, characterized in that:

The irradiation time of each of the plurality of irradiation steps is determined so that the irradiation time is proportional to a power of 2.

5. The multi-charged particle beam drawing method according to claim 2, characterized in that:

In the second group, the timing at which the beams are turned on in the plurality of irradiation steps of the second irradiation time differs for each of the beam groups.

6. The multi-charged particle beam drawing method according to claim 1, characterized in that:

Among the plurality of bundles, bundles adjacent to each other in a drawing progress direction or a direction linearly independent of the drawing progress direction are classified into different groups.

7. A multi-charged particle beam mapping device, characterized in that:

have:

an emission unit that emits multiple beams of charged particles; and

A drawing control unit switches on and off for each of the plurality of beams to control the irradiation time of each of the plurality of beams obtained based on the drawing pattern data;

The above-mentioned depiction control unit grouped the multiple beams constituting the above-mentioned multiple beams into multiple beam groups, divided the above-mentioned each emission into multiple irradiation steps including irradiation steps with different irradiation times, and in a part of the above-mentioned multiple irradiation steps after being divided, grouped multiple irradiation steps with a predetermined first irradiation time into a first group, selected a group of irradiation steps that becomes the irradiation time of each of the above-mentioned beams after the total irradiation time of each irradiation step is determined, and determined the timing of the irradiation step of the above-mentioned first group of the above-mentioned multiple irradiation steps belonging to each of the above-mentioned multiple beam groups based on a predetermined allocation order and the number of the above-mentioned irradiation steps that become connected, so that the timing of the irradiation step of the above-mentioned first group is different for each of the above-mentioned beam groups.

8. The multi-charged particle beam drawing device according to claim 7, characterized in that:

9. The multi-charged particle beam imaging device according to claim 8, characterized in that:

10. The multi-charged particle beam imaging device according to claim 7, wherein:

11. The multi-charged particle beam drawing device according to claim 8, characterized in that:

12. The multi-charged particle beam drawing device according to claim 7, characterized in that:

The drawing control unit classifies, among the plurality of bundles, bundles that are adjacent to each other in a drawing progress direction or a direction linearly independent of the drawing progress direction into different groups.